552 CEXOZOIC TIME. 



not merely the sea-borders, but nearly or quite the whole breadth of 

 the continent, and that its amount was greatest to the north. 



We cannot suppose any damming of the St. Lawrence by ice, in 

 order to account for the terraces of Lake Ontario ; for they are very 

 much higher on the northern side of the lake than on the southern ; 

 and the terrace nearly 500 feet above the St. Lawrence, shell-hearing 

 near Montreal, may be traced along at intervals to the northern bor- 

 ders of the lake, proving unbroken communication at the time, and 

 a vast outflow of water. Admitting the submergence, and its increase 

 in amount northward, the inequality in the level of the terraces on the 

 north and south sides of a lake gives no difficulty. 



We hence learn that, in the Champlain era, salt waters spread over 

 a large coast-region of Maine, and up the St. Lawrence nearly to Lake 

 Ontario, and covered also Lake Champlain and its borders. This 

 great arm of the sea, full 500 feet deep at Montreal and in Lake 

 Champlain, was frequented by Whales and Seals, their remains having 

 been found near Montreal, and a large part of the skeleton of a Whale 

 — Beluga Vermontana Thompson (Fig. 950) — having been dug up 

 on the borders of Lake Champlain, sixty feet above its level, or 150 

 feet above that of the ocean. It appears, besides, that Nova Scotia 

 was, at the same time, an island, and that the Labrador oceanic cur- 

 rent crossed the present isthmus (now less than twenty feet above 

 high tide at Cumberland basin) with a depth of water exceeding 350 

 feet, and thence flowed down the Bay of Fundy to the coast of Maine 

 and eastern Massachusetts. 



We learn, also, that the region of the Great Lakes was probably 

 one immense lake, and that the waters spread far south over the States 

 of Ohio, Indiana, and Illinois, and discharged from Lake Erie and 

 Lake Michigan into the Mississippi valley, so that there was abundant 

 opportunity for transportation, by means of floating ice, from the 

 Glacier to the Gulf. We gather also that the Mississippi waters of 

 the Champlain era, below the mouth of the Ohio, had an average 

 breadth of fifty miles, and, along by Tennessee and northern Missis- 

 sippi, of seventy-five miles ; so that it was indeed a great stream. In 

 the Glacial period, the era of erosion, it was deepening its bed, through 

 the Paleozoic, Cretaceous, and Tertiary rocks ; but, in the Champlain, 

 when the land to the north was depressed, the river filled full the wide 

 valley, and made its great breadth of Champlain deposits. All the 

 other rivers of the continent, alike augmented, were at the same work, 

 each according to its capacity. The Champlain period, in the world's 

 history, was preeminently the era of fresh-water formations. 



Other geographical changes of the Champlain period consisted in 

 the filling up of old river- channels, and forcing the streams to open 



